German patent application No. 26 53 046 (corresponding to U.S. Pat. No. 4,265,200), discloses a process and a device for controlling an injection actuator in a diesel engine.
Injection actuators are also being used in newer injection systems with distributor injection pumps, where essential injection parameters, such as injection start and injection end, can be controlled by using a solenoid valve to influence the start of delivery and/or the delivery rate.
The injection actuator is usually actuated in the "advance" direction by applying pressure to the injection actuator piston. In the "retard" direction, the actuator is actuated by removing pressure via a backflow valve or a backflow throttle. Although the removal of pressure alone allows this retard adjustment, the required restoring force is applied both through a restoring spring and hydraulic forces acting on the actuator piston during injection.
If the vehicle is decelerating, normally no injection takes place and the restoring force component of the injection is no longer needed. Under such operating conditions, the only restoring force applied is that of the restoring spring, which may not be exerted in certain operating ranges. As a result, the injection actuator remains in an incorrect position in those operating ranges. However, intolerable combustion conditions do not occur because no injection takes place.
Since the setpoint and actual positions of the injection actuator are being monitored, error messages indicating a permanent deviation may result. This results in an entry in the system error memory. During servicing, such an entry can lead to unnecessary repair or replacement of the pump. When deceleration ends, an erroneous injection start takes place for a certain number of injections, which may result in smoke release.